1. Technical Field
A contact plug in a semiconductor device and method of forming the same are disclosed, which can prevent an electric field from being concentrated, and method of forming the same.
2. Discussion of Related Art
Conventionally, the peripheral pitch is not critical compared to the cell pitch. As the level of integration in a device increases, however, the peripheral pitch becomes important as much as the cell pitch. For this reason, as the peripheral elements shrink as much as the cell, a metal layer that is difficult to shrink relatively compared to a device composed of polysilicon.
FIG. 1 is a cross-sectional view showing the structure of a contact plug in a semiconductor device in the related art and FIG. 2 is a cross-sectional view of the device taken along lines A–A′ shown in FIG. 1.
Referring to FIG. 1 and FIG. 2, a transistor having a gate 103 and a source/drain 104 is formed in a semiconductor substrate 101. The gate 103 and the source/drain 104 are each connected to metal wires 109a and 109c through contact plugs 107a and 107b, respectively. Meanwhile, metal wires 109b for electrically connecting neighboring other elements are formed around the metal wires 109a and 109c each connected to the gate 103 and the source/drain 104. Unexplained reference numeral 102 indicates an isolation film, and 106 and 108 designate interlayer insulating films.
At this time, as the degree of integration in the device increases, it is required that the junction region of the transistor be connected to the metal wires with only a single contact plug. For example, although the area of the source/drain 104 is wide, various metal wires 109a and 109b are formed on the source/drain 104. Only the metal wire 109a of the metal wires 109a and 109b is connected to the source/drain 104. For this reason, there occurs a case where only one contact plug 107a has to be formed since the width of the metal wire 109a is narrow although the area of the source/drain 104 is wide.
In this case, an electric field (indicated by dotted arrows) is concentrated on the contact plug 107a having a narrow width. This may result in a problem that on-current is reduced compared to a case where several contact plugs are formed.